{"id":2137,"date":"2015-03-02T00:12:39","date_gmt":"2015-03-02T00:12:39","guid":{"rendered":"http:\/\/41j.com\/blog\/?p=2137"},"modified":"2015-03-02T00:12:39","modified_gmt":"2015-03-02T00:12:39","slug":"sem-scanning-electron-microscope-notes","status":"publish","type":"post","link":"https:\/\/41j.com\/blog\/2015\/03\/sem-scanning-electron-microscope-notes\/","title":{"rendered":"SEM (Scanning Electron Microscope) Notes"},"content":{"rendered":"<p>I&#8217;ve been looking at buying an SEM, possibly for shared use and mostly because I&#8217;ve seen a couple going very cheaply and having a microscope capable of 100000x magnification intrigues me.<\/p>\n<p>This post will serve a a location for me to keep my notes on SEMs.<\/p>\n<h2>Sample\/Operation issues<\/h2>\n<p>In general you want to minimize the acceleration voltage, to avoid damaging your sample. However this also results in a poorer resolution image. So there are trade offs to be made in acceleration voltage. The <a href=\"http:\/\/gu.pe\/semguide\/imagedistrubances.html\">JOEL SEM Guide<\/a> has extensive information on the issues involved. The figure below sums up the issues:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/gu.pe\/semguide\/figs1_2.png\" width=\"798\" height=\"308\" class=\"alignnone\" \/><\/p>\n<p>You can see how the applied voltage has effected image resolution in the image below:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/gu.pe\/semguide\/fig3.png\" width=\"774\" height=\"388\" class=\"alignnone\" \/><\/p>\n<p>You also have similar issues with probe current, minimizing probe current yields sharper images (higher resolution) but you lose sharpness (there&#8217;s more noise). High currents can also damage the sample.<\/p>\n<p>The sample angle can also have a significant effect, causing edge effects at certain tilt angles:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/gu.pe\/semguide\/fig12.png\" width=\"370\" height=\"842\" class=\"alignnone\" \/><\/p>\n<p>Another issue that comes up is sample &#8220;charge-up&#8221;. If your sample is an insulator a charge can build up on the surface, which will result in poor image quality:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/gu.pe\/semguide\/fig21.png\" width=\"390\" height=\"696\" class=\"alignnone\" \/> <\/p>\n<p>This can be countered against by using a lower voltage, or by coating the sample with a conductive layer (e.g. <a href=\"http:\/\/gu.pe\/semguide\/operationaltechnique.html\">with a sputtering machine<\/a>).<\/p>\n<h2>EDS\/EDAX<\/h2>\n<p>Some SEMs come equipped with an EDS system (the most popular appears to be the EDAX). This is a <a href=\"http:\/\/en.wikipedia.org\/wiki\/Energy-dispersive_X-ray_spectroscopy\">X-ray spectroscopy<\/a> method mostly used for biological samples. It allows the user to chemically characterize their sample.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>I&#8217;ve been looking at buying an SEM, possibly for shared use and mostly because I&#8217;ve seen a couple going very cheaply and having a microscope capable of 100000x magnification intrigues me. This post will serve a a location for me to keep my notes on SEMs. Sample\/Operation issues In general you want to minimize the [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[1],"tags":[],"class_list":["post-2137","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p1RRoU-yt","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/41j.com\/blog\/wp-json\/wp\/v2\/posts\/2137","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/41j.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/41j.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/41j.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/41j.com\/blog\/wp-json\/wp\/v2\/comments?post=2137"}],"version-history":[{"count":1,"href":"https:\/\/41j.com\/blog\/wp-json\/wp\/v2\/posts\/2137\/revisions"}],"predecessor-version":[{"id":2138,"href":"https:\/\/41j.com\/blog\/wp-json\/wp\/v2\/posts\/2137\/revisions\/2138"}],"wp:attachment":[{"href":"https:\/\/41j.com\/blog\/wp-json\/wp\/v2\/media?parent=2137"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/41j.com\/blog\/wp-json\/wp\/v2\/categories?post=2137"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/41j.com\/blog\/wp-json\/wp\/v2\/tags?post=2137"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}